Manually controlled electro-hydraulic system for aircraft



March 18, 1958 s, G. GLAZE ETAL 2,826,896

' MANUALLY CONTROLLED ELECTRO-HYDRAULIC SYSTEM FOR AIRCRAFT Filed Dec. 14, 1955 A .NSN

ESS. MS

nited States ate lVlANUALLY CONTROLLED ELECTRO-HYDRAU- LIC SYSTEM FOR AIRCRAFT Stanley George Glaze, Brierley Hill, England, and Charles Philip Smith, Ramsey, Isle of Man, assignors to H. M. Hobson, Limited, London, England, a British company Application December 14, 1955, Serial No. 553,130

Claims priority, application Great Britain December 17, 1954 This invention relates to a power operated flying control system for aircraft of the kind in which a pilots control member controls by means of an electrical signalling system the position of the input member of a servo motor for actuating a control surface of the aircraft.

With a view to safeguarding against the contingency of failure of electrical signalling systems, the invention provides a system of the above kind in which the servo motor is constituted by a tandem hydraulic jack, each section of said jack having at least two independently movable control valves each of which is actuable by the pilots control member through the agency of an associated electromechanical transducer mechanism.

This system has the advantage that, as explained later if a control valve of one section of the jack should stick in an open position the other control valve of that section together with the control valves of the other section of the jack assume positions that will cancel a tendency of the servo motor to run away on a resultant output load basis.

Preferably, as in the case of the system described in U. S. application Serial No. 553,124, led December, 14, 1955, the p ilots Acontrol member is arranged to operate at least three electrical signalling systems, the signals from all the signalling systems being fed to each of the transducer mechanism. In the event of an electrical failure in one signalling system the other two will then be able to exert majority control over all of the control valves.

One embodiment of the invention will now lbe described in more detail, by way of example, with reference to the accompanying drawing in which:

Fig. l is a diagram showing the servo motor and associated electrical signalling systems,

Fig. 2 is a circuit diagram and Fig. 3 is a front view of one of the transducers with its cover plate removed.

The control surface 1 is operated by a tandem hydraulic jack comprising fixed pistons 2, 2A accommodated in cylinders 3, 3A in a movable cylinder block 4 coupled to the control surface. The two sections of the jack are respectively controlled by control valves 5, 5 and 5A, SA associated with pressure inlets 15, 15', 15A and 15A and exhaust outlets 11, 11', 11A, 11'A. The control valves, on movement from the neutral position shown, establish in well known fashion alternative pressure and exhaust connections to the ends of the two sections of the jack to cause the cylinder block 4 to move in a direction and to an extent determined by the movement of the control valves.

The control valves are actuated by electromechanical transducers 6, 6', 6A, 6A respectively. The transducers are of the character described in U. S. application Serial No. 549,737, tiled November 29, 1955, and each comprises as shown in Fig. 3 a rotary armature 2t) coupled 'ice to the associated control valve by an arm 21 and a link 22 and movable between two pole pieces 23 around which are wound three coils 12, 13, 14. The pilots control lever 7 actuates, when displaced, potentiometers 8, SA, SB of three electrical signalling systems including amplifiers 9, 9A, 9B. The signals from all the amplifiers are fed, as shown, to each of the transducers. Thus the signals from the amplifier 9 are fed through the coils 12, 12A, 12A and 12' in series. Potentiometers 10, 10A, 10B actuated by movement of the cylinder block 4 provide feed back signals to the amplifiers. l

As shown in Fig. 2, each electrical signalling system includes an individual source of electric power indicated diagrammatically by a battery 13, for energising the amplifier 9 and its associated Potentiometers 3, 10. Pick- Ols 16, 16A, 16B actuated by the control member 6 coact with the potentiometers 8, SA, 3B and pick-offs 17, 17A, 17B actuated by the cylinder 4 coact with the potentiometers 10, 10A, 10B.

If desired, signals may also be fed to the transducers via the ampliliers 9, 9A and 9B from an auto-pilot and/ or from an auto-stabilizer. Also, provision may be made as described in British application No. 36147/54 for reversion to mechanical control of the jack by the pilot in the event of an emergency.

It is necessary that each of the ampliers 9, 9A, 9B should saturate at an input level proportional to a misalignment between the input and output members of the servo motor small in relation to the total stroke of the output member.

If desired, each of the three-coil transducers illustrated may be replaced by three single-coil transducers, each fed from one of the ampliiers. Also, the transducer mechanisms may, if desired, be fed with signals from more than three electrical signalling systems operable by the pilots control member.

Again each section of the jack may be provided with more than two independently movable control valves, each of which is actuable by the pilot through the agency of an associated electro-mechanical transducer mecha.-A

nism. Moreover, four or more electrical signalling systems may be provided, signals from all of the electrical systems being fed to each of the transducer mechanisms. Thus each section of the jack could have three control valves, each actuated by a four-coil transducer receiving signals from four electrical systems operable by the pilots control member.

The number of control valves per section of the jack must be at least two and may either be equal to or may exceed the number of electrical signalling systems.

'I'he operation of the system is as follows:

On movement of the pilots lever 7 corresponding signals are sent from the potentiometers S, 8A, 8B to the corresponding amplifiers 9, 9A, 9B. Each of the electrical signalling systems then sends from its associated amplifier signals to all of the transducers 6, 6A, 6'A and 6' demanding movement of their associated control valves 5, 5A, S'A and 5 in the direction corresponding to the direction of movement of the pilots lever 7. The amplifier 9 supplies such signals to the coils numbered 12, the amplifier 9A to the coils numbered 13 and the amplifier 9B to the coils numbered 14 as will be clear from Fig. 1. As the result of movement of the four control valves 5, 5A, SA and 5 the cylinder block 4 of the jack moves in the same direction as the control valves to eifect appropriate movement of the control surface 1. As the result, the potentiometers 10, 10A, 10B send feed back signals to the amplifiers 9, 9A, 9B and, when the control surface l has assumed the position demanded by the pilots lever 7 the control valves are returned, by the transducers under control of the amplifiers, to their neutral position,

illustrated i in Fig 1, t to-prewentffurthermovement4 of-the of the transducers viathe coils numbered12, so enabling thepilot toretain control over the jack. Evenif a `fault shoulddevelop in one of the electrical signalling systems, e. g. that associated with'theampliter-QB; which results in transmissionto the coils numbered 14vdema-nd ing movement of the-control valves inthe reversedirection to that selected by the pilot, the coils-numberedA 12 and 13of each transducer which receive `signa-ls'irorn the still effective electrical systems will be able-to overpower the defective coils numbered 14 and ensurevthat'thescontrol valveswill be moved in the correct direction;

Whatwe claim as our invention and'desire to secure by Letters Patentis: i

1. A` poweroperated 'flying control systerntor aircraft, comprising a control surface, a tandemhydraulie'jack comprising two cylinders, a piston in-each cylinder, apiston rod connecting-said pistons, and at least=two independently movable controlrvalves adjacentto-eachacylinder and controlling the admissionloffluidi thereto and the exhaust of fluid therefrom, means actuated-by relative movement of said vcylinders and pistonsfor-imparting movementto said controlsurface, a plurality lofelectromechanical transducer mechanisms,4 onefor operating each control valve, a pilotscontrolmemberiand an-electrical signalling system connected to` allfofsaidtransk ducer mechanisms and operable by-saidv control member to transmibsignals to'all of-said transducer mechanisms and thereby to actuate saidjaclr to-positionsaidfcontrol surface in-correspondencewith-the position of the-controlmeruber.

asaesa i 2. A power operated flying control systemfor aircraft, comprising a control surface, a tandem hydraulic jack comprising two cylinders, a piston in each cylinder, a piston rod connecting said pistons, and at least two independently movable control valves adjacent to each cylinder and controlling the admission ofk Huid thereto and the exhaust of uid therefrom, means actuated by relative moyementof said cylinders and pistons for imparting movement to saidcontrol surface, aplurality of electromechanical'A transducer` mechanisms, one for operating each control valve, a pilots control member and atleast three electrical signalling systems, each of said signalling systems lbeing connectedfto send signals under controlot the pilot to al1 ofthe transducer mechanisms and all of said signalling systems being operablein common by the pilots control member to transmit ,signals to all of said transducer mechanismsfand thereby to actuate said jack to position` said control surface in correspondence with the position of the ,control member.

3. A system-as claimed in claim2, in which each transducer mechanism comprises a movable armature connected totheassociated control valve and a plurality of coils controlling the position oflsaid armature, each coil being connectedto and receiving signals from one of said signallingisystems.

4. A system as claimedin claim `2, in which each .electrical signalling system comprises an amplifier, a pair of potentiometers, an individual source; of velectric power for energizingsaid amplier and said potentiometergmcans operated ,by the, control member. for,Y adjusting, one potentiometer to sup ply finput` signals to the amplifier and means actuated byftheflack forgadjusting thefothervpotentiometer, -to-supply feedback;signals` to the, ampliier.

References A CitedV imthe leof this -patent UNITED, STATES PATENTS,

2,528,645 Edwards Nov. 7, 1950 2,597,420 Westbury May 20, 1952 2,628,594 Teague Feb. 17, `1953 2,658,701 Robertson Nov. 10, 1953 

